Biomedical Applications of Opto-Thermal Heating and Ultrasound

Abstract

This thesis describes two projects in which electrical engineering is applied towards biomedical applications. The first project involves the development of an opto-thermocapillary microrobot system. These gas-bubble microrobots are capable of manipulating cells or micro-objects, and are controlled using computer-generated holograms from a spatial light modulator (SLM). A program was developed in LabVIEW allowing for the automatic actuation of these microrobots in parallel without the need of a human operator. Two major functions have been implemented in this program. The first is a system that prevents microrobots from colliding with one another. The second function is a sequence generator that allows a user to create paths for the actuation of multiple microrobots over a programmable amount of time. The sequence generator creates the necessary holograms and sends them to the SLM, thus controlling the microrobots. With this program, the microrobots were successfully able to automatically manipulate and assemble micro-objects. The second project explores the feasibility of an ultrasonic bone-marrow harvester. This device uses a piezoelectric actuator enclosed in a concave casing to generate focused ultrasound that can disrupt bone marrow. Pressure maps of the measured output of the device were created, with a maximum positive peak pressure of 0.190 MPa and a maximum negative peak pressure of 0.176 MPa at the center of the device. Experimental data indicates that 100-ms of ultrasound exposure is able to disrupt the cellular matrix of red bone marrow, resulting in up to 28.1% less force needed to penetrate marrow. At the same time, viability of peripheral cells remains high, between 92 to 95% for yellow marrow. This shows the potential of using an ultrasonic device to disrupt bone marrow for eventual harvesting.